As a naturalized citizen, he does have rights - or is supposed to. It's not the same as bombing a US citizen who's actively helping the enemy overseas - this guy was caught HERE.
Even Timothy McVeigh had a lawyer - and in his case, justice was ultimately served.
Now I saw on TV they're thinking of charging him with use of a " . . . weapon of mass destruction."
I've always understood WMDs to be nuclear, chemical, or biological; so nukes and dirty bombs, poison gas, germ warfare, etc. would qualify as WMDs, whereas a common explosive would not. Don't like this expansion of the definition of WMD.
As to what this guy gets charged with . . . three counts of Murder 1 with special circumstances (if the provision is in MA law), MANY counts of attempted murder, aggravated assault, assault with a deadly weapon, possession of destructive devices, etc., probably even Treason if a connection with foreign terrorist organizations can be shown. Seems to be PLENTY of opportunity to legitimately hit him with half the penal code for what he did without any WMD nonsense. In general terms, they should just proceed the way they did with McVeigh.